In a liquid crystal display device, even if a drive voltage to be applied to liquid crystal is constant, the contrast changes depending upon an ambient temperature environment. Japanese Patent Application Laid-Open No. 10-31204 discloses an LCD which detects a temperature of a liquid crystal panel by means of a temperature sensor such as a thermistor and automatically adjusts a drive voltage to be applied to the liquid crystal panel based on the detected temperature.
In the liquid crystal, its phase is solidified under the low temperature environment and its response characteristics are lowered. When a liquid crystal panel is used in a vehicle-use display device, an alignment transition of the liquid crystal cannot track a change in a measured value at a vehicle speed or an engine speed that an update period of the display value is short. As a result, an overlap occurs and visibility is remarkably deteriorated. In order to solve such a technical problem, a liquid crystal display device containing a panel heater for heating a liquid crystal panel is also suggested.
When the heater is provided in order to secure the response characteristics of the liquid crystal under the low temperature environment, since the heater consumes a lot of power, a wiring capacity and a battery capacity should be enlarged. Therefore, it is difficult to apply this display device to a vehicle such as a two-wheeler where weight and a battery size are limited. Moreover, if the heater is contained in a portion such as a meter unit of the two-wheeler where its size is limited, there arises a new technical problem that other parts should be further miniaturized.
It is an object of the present invention to provide a vehicle-use liquid crystal display device which is capable of securing high visibility even under a low temperature environment without increasing power consumption and enlarging its size.